1. Field of the Invention
The present invention relates to an information processing apparatus, a communication system, and a communication method.
2. Description of the Related Art
Conventionally, a method for connecting a plurality of communication networks via an ANI (Application Server Network Interface) is known (for example, see Japanese Laid-open Patent Publication No. 2010-178178). According to the conventional method, separate communication networks are connected with each other via the ANI and an inter-network communication is realized. The ANI is sometimes called an SNI.
Meanwhile, IPv6 (Internet Protocol version 6) is known as a communication protocol to resolve the problem of the IP address exhaustion in IPv4 (Internet Protocol version 4), which is a widely-used communication protocol for a communication network such as the Internet. In recent years, Next Generation Networks (NGN) using IPv6 are constructed. In connecting the NGN to a server that provides various communication services, the method using the ANI is employed.
When the IPv6 is introduced into an existing network of IPv4, usually a network using IPv6 and a network using IPv4 are built side by side. To realize the communication in both IPv4 and IPv6, a computer to which an IP address of IPv4 is assigned is further assigned with an IP address of IPv6.
However, when IP addresses of IPv6 are merely assigned to computers of an existing communication network, a problem may occur in communication between computers via an NGN in some cases.
FIG. 9 is a schematic diagram illustrating an example in which communication cannot be established by an NGN using IPv6.
In the example of FIG. 9, a public communication network 1000 employs IPv4 as its communication protocol. Then, a server 1001 of the public communication network 1000 is newly assigned with an IP address of the IPv6, so that IPv6 can additionally be used as the communication protocol. In this case, the server 1001 has both the IP address of IPv4 and the IP address of IPv6. A communication network n1 illustrated in FIG. 9 is a communication network of IPv6 serving as the public communication network 1000 and a communication network n2 is a communication network of IPv4.
As illustrated in FIG. 9, a Next Generation Network 2000 in which IPv6 is used as an internal communication protocol is present aside from the public communication network 1000. Here, the Next Generation Network 2000 based on IPv6 is a communication network independent from the IPv6 communication network in the public communication network 1000. That is, the Next Generation Network 2000 is a closed communication network. In other words, a terminal 2001 connected to the Next Generation Network 2000, which is independent from the public communication network 1000, cannot perform communication using IPv6 with the server 1001 to which the IP address of IPv6 is assigned in the public communication network 1000.
On the other hand, the terminal 2001 is configured to be connectable to the public communication network 1000 through communication of IPv4.
In the general communication network, a DNS (Domain Name System) server is provided. For example, in the example of FIG. 9, a DNS server 1501 is provided in the public communication network 1000 and a DNS server 1502 is provided in the Next Generation Network 2000. When the DNS server receives an inquiry of an IP address by designation of an URL (Uniform Resource Locator) from each terminal, the DNS server 1500 transmits information indicating an IP address corresponding to a host name of the designated URL to the terminal having queried the IP address. Here, when the designated URL is a URL of a server to which both an IP address of IPv4 and an IP address of IPv6 are assigned, the DNS server transmits both the IP address of IPv4 and the IP address of IPv6 to the terminal.
Each terminal makes a request for establishing communication using the IP address transmitted from the DNS server 1500. When both the IP address of IPv4 and the IP address of IPv6 are transmitted from the DNS server, the terminal first performs a process of establishing communication of IPv6. When the communication of IPv6 is not established, the terminal performs a process of establishing communication of IPv4. In the example of FIG. 9, a terminal 1002 connected to the public communication network 1000 by both IPv4 and IPv6, can establish a communication of IPv6 with the server 1001 without a problem.
On the other hand, as described above, the terminal 2001 first attempts to perform communication of IPv6 with the server 1001 though the communication cannot be established by IPv6 between the server 1001 of the public communication network 1000 and the terminal 2001. Therefore, a waiting time from confirmation of a failure of the communication of IPv6 to transition to the communication of IPv4 may occur. A series of processes in which the waiting time occurs is called “fallback.” Since the fallback causes deterioration in a response in use of a communication service from the terminal 2001 inside the Next Generation Network 2000, the fallback is a problem.
To prevent the fallback, it is possible to provide another, separate server connected to the Next Generation Network 2000. However, in this case, since both the server 1001 of the public communication network 1000 and the other server inside the Next Generation Network 2000 are provided, installations and administration cost may be doubled, thereby resulting in considerable ineffectiveness.
Alternatively, it may be possible to distinguish the terminal 1002 connected to the public communication network 1000 from the terminal 2001 connected to the Next Generation Network 2000 based on the IP address assigned to each terminal, and to control the terminal 2001 such that the terminal 2001 does not perform a process of establishing connection of IPv6 when trying to establish connection with the public communication network 1000. However, this method has problems in that an additional mechanism is required to identify each terminal and the fallback may not be prevented in a terminal of which a connection path is unclear.
Accordingly, when the communication of IPv6 is performed, a mechanism is required to establish the connection of IPv6 between mutually independent communication networks, such as the public communication network 1000 and a closed communication network such as the Next Generation Network 2000.
The problems described above in relation to the IPv6 are not problems peculiar to IPv6. Similar problems may occur when communication realized by any new communication protocol is introduced into an existing communication network.